Patch environment for VCS rather than creating new one

Closes #240

CHANGELOG.md

@@ -1,5 +1,9 @@
 # Changes
 
+Unreleased
+
+* Patch environment for VCS subprocesses rather than generating a new one
+
 2018-02-19 (version 0.4.9)
 
 * Fix root user segment

powerline_shell/segments/bzr.py

@@ -11,7 +11,9 @@ def get_PATH():
 
 
 def bzr_subprocess_env():
-    return {"PATH": get_PATH()}
+    env = dict(os.environ)
+    env.update({"PATH": get_PATH()})
+    return env
 
 
 def _get_bzr_branch():

powerline_shell/segments/fossil.py

@@ -11,7 +11,9 @@ def get_PATH():
 
 
 def fossil_subprocess_env():
-    return {"PATH": get_PATH()}
+    env = dict(os.environ)
+    env.update({"PATH": get_PATH()})
+    return env
 
 
 def _get_fossil_branch():

powerline_shell/segments/git.py

@@ -12,17 +12,16 @@ def get_PATH():
 
 
 def git_subprocess_env():
-    return {
+    env = dict(os.environ)
+    env.update({
         # LANG is specified to ensure git always uses a language we are expecting.
         # Otherwise we may be unable to parse the output.
         "LANG": "C",
 
-        # https://github.com/milkbikis/powerline-shell/pull/126
-        "HOME": os.getenv("HOME"),
-
         # https://github.com/milkbikis/powerline-shell/pull/153
         "PATH": get_PATH(),
-    }
+    })
+    return env
 
 
 def parse_git_branch_info(status):

powerline_shell/segments/hg.py

@@ -11,7 +11,9 @@ def get_PATH():
 
 
 def hg_subprocess_env():
-    return {"PATH": get_PATH()}
+    env = dict(os.environ)
+    env.update({"PATH": get_PATH()})
+    return env
 
 
 def _get_hg_branch():

powerline_shell/segments/svn.py

@@ -10,7 +10,9 @@ def get_PATH():
 
 
 def svn_subprocess_env():
-    return {"PATH": get_PATH()}
+    env = dict(os.environ)
+    env.update({"PATH": get_PATH()})
+    return env
 
 
 def _get_svn_revision():